usage description of docker deploy in md not consistant with go file

Signed-off-by: lixiaobing10051267 <li.xiaobing1@zte.com.cn>

experimental/docker-stacks-and-bundles.md

@@ -41,7 +41,7 @@ A stack is created using the `docker deploy` command:
 
 Usage:  docker deploy [OPTIONS] STACK
 
-Create and update a stack
+Create and update a stack from a Distributed Application Bundle (DAB)
 
 Options:
       --file   string        Path to a Distributed Application Bundle file (Default: STACK.dab)